Japanese Laid-Open Patent Publication No. 2012-188858 describes a conventional sliding plug door device for a railway vehicle. The plug door device includes a plug door opening-closing apparatus that performs an operation for moving a door panel in the widthwise direction of a railway vehicle when sliding the door panel in the front-rear direction of the railway vehicle, that is, the so-called plugging operation. The plug door device further includes a fixed base and a movable base. The fixed base includes a front rail and a rear rail. The movable base includes a front roller and a rear roller respectively coupled to the front rail and the rear rail. The plug door opening-closing apparatus is mounted on the movable base. The front rail and the rear rail are fixed to a side wall of the vehicle body so that the plug door opening-closing apparatus is held in between in the front-rear direction. Each rail extends in the vehicle width direction. The movable base is movably supported by the two rails on the fixed base. When force that presses the movable base in the vehicle width direction is applied to the movable base, the front and rear rollers roll on the front and rear rails. This moves the movable base and the door panel relative to the fixed base in the vehicle width direction.